On Thu, 21 Apr 2016 12:48:50 +0200 Heiko Schocher hs@denx.de wrote:
Hello Boris,
Am 21.04.2016 um 12:25 schrieb Boris Brezillon:
Hi Heiko,
On Thu, 21 Apr 2016 12:09:34 +0200 Heiko Schocher hs@denx.de wrote:
Hello Boris,
Am 21.04.2016 um 10:58 schrieb Boris Brezillon:
On Tue, 2 Feb 2016 11:54:35 +0100 Heiko Schocher hs@denx.de wrote:
Set free_count to zero before walking through ai->erase list in wl_init().
As U-Boot has no workqueue/threads, it immediately calls erase_worker(), which increase for each erased block free_count. Without this patch, free_count gets after this initialized to zero in wl_init(), so the free_count variable always has the maybe wrong value 0.
Detected this behaviour on the dxr2 board, where the UBI fastmap gets not written when attaching/dettaching on an empty NAND. It drops instead the error message:
could not find any anchor PEB
With this patch, fastmap gets written on dettach.
I ran into the same problem, and produced the exact same patch to fix it, so
Reviewed-by: Boris Brezillon boris.brezillon@free-electrons.com
Thanks!
I did not yet found time, to investigate this problem deeper, sorry.
The real reason to me seems, on an empty nand flash, we call scan_all() which calls scan_peb() which calls ubi_io_read_ec_hdr() which returns UBI_IO_FF as the nand is empty.
This adds the PEB to the erase list, and here comes the difference between U-Boot and linux, we have no threads in U-Boot, so we call the erase_worker function immediately ... which increments the "ubi->free_count" variable ... after that it get set to "ubi->free_count = 0" ... which leads into the error we see ...
No idea, if the correct fix not would be to move this erase_worker call after the attach phase ended, as Richard suggested, or if this fix is also valid ...
I discussed that with Richard, and I think moving the ->free_count assignment before iterating over the ->erase list is a good solution.
Ah! Ok, than its fine for me too.
I know the Linux code is assuming that the UBI thread is not launched yet when we call ubi_wl_init(), but to me it seems a bit risky to rely on this assumption (what if we do the UBI thread creation a bit earlier for some reason?). And, of course, as you explained, uboot does not know anything about threads, so all UBI works are executed synchronously, which makes this implementation buggy in uboot.
Hmm... is it also a valid fix for linux then?
Well, it's not required, but it's making the code more future proof IMO. So again, I'll let Richard decide on this aspect.